hair cells are innervated by both afferent and efferent fibres
afferent fibres to the outer hair cells are not shown in this figure
efferent fibres innervating the organ of Corti have their cell bodies in the brainstem, and are part of a reflex circuit via collateral connections arising from the cochlear nucleus
medial efferents form large synapses with the cell bodies of the outer hair cells
lateral efferents innervate the afferent terminals underlying the inner hair cells
descending control of the OHCs allows for reflex control of basilar membrane motion
activation of efferent fibres via stimulation of the contralateral ear (filled circles) causes an increase in acoustic thresholds
i.e., the presence of sound in one ear means that it takes a louder than normal sound in the opposite ear in order to produce the same amplitude of basilar membrane motion --- the normal graph (open circles) shifts to the right
